The present invention relates to an image processing apparatus and an image processing method, which synthesize images of a plurality of frames different in exposure value and create a synthetic image in which a dynamic range is expanded.
While the human sense of sight has an extremely wide dynamic range, a dynamic range of an imaging device such as a video camera is narrow. Therefore, in the case of simultaneously imaging a main subject such as a person and a background, then sometimes, the main subject and the back ground are imaged in a different state from appearances thereof such that the main subject is imaged so as to be dark and that the background is imaged so as to be subjected to over exposure. Accordingly, a technology has been known, which is for expanding a dynamic range of an image by imaging the same subject plural times under different conditions where an exposure value is differentiated, and by synthesizing such images of a plurality of frames.
In the case of synthesizing the images of the plurality of frames and creating such an image with a wide dynamic range, it is necessary to match pixel values of the respective images as synthesis targets based on an exposure value ratio at an imaging time. However, in actual imaging, it is necessary to image the images in a set exposure value ratio, and the pixel values become discontinuous at boundary portions where the images of the plurality of frames are switched in the case where the images concerned are synthesized. Technologies for reducing such discontinuity of the pixel values at the boundary portions are described in Japanese Patent Laid-Open Publication No. 2002-223350 (Patent Literature 1) and Japanese Patent Laid-Open Publication No. 2010-273001 (Patent Literature 2).